Sensing cylinder

ABSTRACT

A steering system for a vehicle having a pair of steerable axles and an operator&#39;&#39;s station at each end. The system provides a means for steering the vehicle from either station and provides a means for selectively steering the vehicle in any one of three different modes.

United States Patent 1191 11] 3,765,306 Luft 1 Oct. 16, 1973 1 SENSINGCYLINDER 3,190,185 6/1965 Rasmussen 92/131 Inventor: Rabe" G wildwood, L3,537,355 11/1970 BllSS 92/131 [73] Assignee: International HarvesterCompany,

Chicago, 111. Primary Examiner-Paul E. Maslousky [22] Filed: Dec. 21,1971 Attorney-Floyd B. Harman [21] Appl. No.: 210,376

Related US. Application Data [62] Division of Ser. No. 52,940, July 7,1970, abandoned. 7 ABSTRACT [52] US. Cl. 92/117 A, 92/131, 92/155 A stng yst f r a hicle having a pair of Steer- [51] Int. Cl. F01b 31/10,FOlb 15/02 able axles and n p r r st ion at each end. The [58] Field ofSearch 92/131, 117 R, 1 17 A; system provides a means for steering thevehicle from 91/360 either station and provides a means for selectivelysteering the vehicle in any one of three different References Citedmodes.

' UNITED STATES PATENTS 2,110,213 3/1938 Flowers 92/131 5 Claims, 4Drawing Figures @B 9 oz 04 11* 1] PATENTED 0U 16 I975 SHEET 2 BF 3 NewNM p 1 m2 ozw a $6 q NW NM %\m NM %N% W \m \1 E Mm an .wmw mw pl. mNm mg.3 mfi N 3 Ohm, mm NQ w 8m 8m ym M w o 2 w NWILIJ +205 W0 0N ANA. Q 00%NQ mow PAIENTED 0B1 16 I973 SHEET 3 OF 3 w N Q NM W 1 SENSING CYLINDERCROSS REFERENCE TO RELATED APPLICATION This is a division of applicationSer. No. 52,940, filed July 7, 1970, now abandoned.

This application is related to that disclosed and claimed in theapplication of Robert G. Luft and Edward A. Bott entitled DRIVE TRAINFOR LOW PROFILE VEHICLE, Ser. No. 796,371 filed Feb. 4, 1969, now US.Pat. No. 3,614,989.

BACKGROUND AND SUMMARY OF THE INVENTION In certain large vehicles, suchas those utilized to tow the jumbo jet aircraft, the size of the machinerequires a control compartment or operators station at each end thereof.Such dual operator stations are provided so that the operator may bepositioned the forward end of the vehicle regardless of its direction oftravel, thus providing the operator with optimum visibility in thatdirection. These dual stations impose a requirement for steering thevehicle from two different locations. Since vehicles of this type aremaneuvered in close proximity to aircraft, damage to which must beavoided, it is highly desirable to permit the operator to selectdifferent modes of steering for the vehicle. This is especiallyadvantageous when the vehicle itself is quite large and the turningradius with only one mode of steering may, in some situations, be toolarge, and in other situations, may be too sharp. 7

It is an object of this invention to provide a sensing cylinder for thesteering system on a vehicle having plural mode steering capabilitywhich will automatically return the wheels to a straight-ahead positionwhen a mode of steering is selected which dictates such an attitude.

Another object is to provide a sensing cylinder which both assists theinitiation of steering and controls the position of a valve directinghydraulic fluid to the steering rams.

A further object of this invention is to provide a sensing cylinderwhich offers minimum resistance to movement from a static position.

These, and other objects of the present invention, and many of itsattendant advantages, will become more readily apparent upon a perusalof the following description and the accompanying drawings, wherein:

FIG. 1 is a schematic representation of a steering system according tothe present invention;

FIG. 2 is a schematic view of a preferred arrangement for providinghydraulic fluid under pressure to the steering rams;

FIG. 3 is a cross sectional view of a preferred embodiment of sensingcylinder utilized in the system shown in FIG. 1; and

FIG. 4 is a cross sectional view taken on line 44 of FIG. 3.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. 1, avehicle, not shown but which may be of the type disclosed in patentapplication Ser. No. 796,371 filed Feb. 4, 1969, is provided with acontrol compartment or operators station at the front, indicatedgenerally at 10, and a similar station 12 at the rear of the vehicle.The front station includes a hand pump 12 connected with and operated bya steering wheel 14. The rear station has a similar hand pump 212connected with and driven by the steering wheel 214. Conduits 16 and 18connect with the hand pump 12 and with one of the hand pump selectorvalves 20 and 22, respectively. Conduits 216 and 218 connect with thehand pump 212 in the rear station and with the hand pump selector valves20 and 22, respectively. The valves 20 and 22 are of the three-port,two-position type, with their positions selected by a position cylinder24, which includes a piston 26 connected with the valves 20 and 22. Aspring 28 biases the piston 26 to the position shown in FIG. 1, whichposition renders the rear hand pump 212 inoperable since the conduits216 and 218 are blocked by the valves 26 and 22. In this position, theconduit 16 communicates with a conduit 30 connected with a hydraulicactuator 32 and the conduit 18 communicates with'a conduit 34 connectedwith a hydraulic actuator 36.

The position of the piston 26 within the cylinder 24 is determined bythe station selector valve 38 located in the front station 10. Thestation selector valve 38 is of the four-port, two-position type andconnects with a reservoir 40 containing air under pressure through aconduit 42. Conduits 44 and 46 connect with the selector valve 38 asdoes a conduit 48 which is vented to atmosphere. Branch conduit 47connects with the conduit 46 and with the cylinder 24. With the stationselector valve positioned to select the front station, as shown in FIG.1, the conduits 47 and 46 are vented to atmosphere through conduit 48.This permits the spring 28 to shift the piston 26 toward the right asviewed in FIG. 1 connecting the conduits 16 and 18 from the front handpump 12 with the conduits 30 and 34. When the station selector valve 38is shifted to the right as viewed in FIG. 1 to permit steering controlby the steering wheel 214, the conduit 44 is connected with the exhaustconduit 48 and pressure from the reservoir 40 is permitted to flowthrough conduits 46 and 47 to the cylinder 24. Pressure acting'on thepiston 26 will shift the piston and both valves 20 and 22 to the left.In this position the valves 20 and 22 block the conduits 16 and l8-andconnect the conduits 216 and 218 with the conduits 30 and 34,respectively.

Regardless of which station has been selected by manipulation of thestation selector valve 38, hydraulic pressure will appear in one of theconduits 30 and 34 depending upon the direction of rotation of thesteering wheel 14 or 214 in the selected station. The hydraulicactuators 32 and 36 are connected with a threeposition directional flowvalve 50. Hydraulic fluid under pressure is provided to the valve 50from a reservoir 52 by a hydraulic pump 54 which communicates with thevalve 51) through a conduit 56. A return conduit 57 connects with thevalve 50 and the reservoir 52. Each of the conduits 58 and 60 arebranched to permit connection with each of two mode control valves 62and 262 when the rotation of either of the pump 12 or 212 provideshydraulic pressure in conduit 30 the hydraulic actuator 32 will shiftthe direction flow valve 50 to the right, i.e., to the right of theposition shown in FIG. 1, in which the conduit 56 will be connected withthe conduit 60 and the conduit 58 with the conduit 57. When the rotationof either of the hand pumps 12 or 212 is in a direction to providehydraulic pressure in line 34, the hydraulic actuator 36 will shift thedirec tion flow valve 50 to the left as viewed in FIG. 1, whereinconduit 56 will be connected with conduit 58 and conduit 60 will beconnected with conduit 57.

The mode control valves 62 and 262 are of the threeposition, four-porttype and their position is determined by mode control cylinders 64 and264. Each of the mode control cylinders 64 and 264 are provided withpistons 66 and 266 which are connected with the mode control valve 62and 262, respectively. The piston 66 is urged toward a centered positionwithin the cylinder 64 by means of springs 68 and 69, while the piston266 is urged toward a center position within its cylinder 264 by meansof springs 268 and 269. Each of the pistons 66 and 266 are capable ofassuming three different positions within the cylinder. That is, eachcan be centered, fully extended or fully retracted. The position of themode control cylinders is determined in part by the station selectorvalve 38 and in part by a mode selector valve 70 which is located in thefront station or by the similar mode selector valve 270 located in therear station 12.

Each of the mode selector valves 70 and 270 are of the three-position,four-port type and when centered provide for two wheel steer from thewheels adjacent the operators station selected by the station selectorvalve 38, and are shiftable from the centered position in one directionto provide crab steering of all four wheels and in the other directionto provide coordinated steering of all four wheels. The mode selectorvalve 70 is operable only when the station selector valve 38 ispositioned for front station operation, while the mode selector valve270 is operable only when the station selector valve 38 has been movedto the rear position. When the station selector valve is in frontposition, as shown in FIG. 1, air pressure is provided from the airreservoir 40 through the conduits 42 and 44 to a conduit 72 whichconnects with the conduit 44. Conduit 72 connects with a double-seated Tconnector 74 containing a ball check valve 76. A conduit 78 communicateswith the T connector 74 at a point intermediate the two seats and withthe head end side of the cylinder 64. The presence of air pressure inthe head end side of the cylinder 64 will cause the piston 66 to beshifted to the right against the bias of the spring 69. Regardless ofthe position of the mode selector valve 70, the piston 66 in the modecontrol cylinder 64 will be in its extended position since air pressureis directed to the head end side of the cylinder by the station selectorvalve 38. The mode selector valve 70 then is utilized to direct pressureselectively to either end of the mode control cylinder 264 in order todetermine what mode of steering will be utilized. In the position shownin FIG. 1, the mode selector valve has been centered so that the conduit44 which receives air pressure from the reservoir 40 has been blocked.Two conduit 80 and 82 connected with the mode selector valve 70 are incommunication with a conduit 84 which exhausts to atmosphere. Theconduit 80 connects with a doubleseated T connector 86 having a ballcheck valve 88. A conduit 90 communicates with the T connector at apoint intermediate the seats and with the rod end side of the modecontrol cylinder 264. The conduit 82 connects with the head end side ofthe cylinder 264. With both the conduits 90 and 82 being exhausted toatmosphere through the conduit 84, the springs 268 and 269 within thecylinder 264 will cause the piston 266 to be centered. When the modeselector valve 70 is moved to the crab position, or to the left asviewed in FIG. 1, conduit 44 will be connected with the conduit 80 whilethe conduit 82 will be exhausted to atmosphere through the conduit 84.Air pressure will be directed through the conduits 42, 44, 80 and 90 tothe rod end side of the cylinder 264. The head end side of the cylinderwill be exhausted to atmosphere through the conduits 82 and 84. Thepresence of high pressure in the rod end side of the cylinder will causethe piston 266 to be retracted moving the mode control valve 262 to theright as viewed in FIG. 1. When the mode selector valve is moved to thefour-wheel position, the conduit 44 will be connected with the conduit82 while the conduit will be exhausted to atmosphere through the conduit84. Air pressure will therefore be directed through the conduit 82 tothe head end side of the cylinder 264 causing the piston 266 to beextended and the mode control valve 262 to be moved to the left.

The mode selector valve 270 in the rear station 12 is provided with anexhaust conduit 284 and with a conduit 272 which communicates with the Tconnector 74 opposite the connection of the line 72 therewith. Anotherconduit 278 connects with the valve 270 and with the rod end side of thecylinder 64. With the station selector valve in the front position,manipulation of the mode selector valve 270 will be completelyineffective because the conduit 46 is connected with atmosphere throughconduit 48 and the presence of air pressure in the conduit 72 will causethe ball 76 to seat against the conduit 272. When the station selectorvalve 38 is moved to the rear position air pressure will be directed tothe conduit 46 and to a conduit 272 which connects with the conduit 46and with the T connector 86 on the side opposite the connection of theconduit 80 therewith. The presence of air pressure in the conduit 272will seat the ball check valve 88 against the conduit 80 and permit airpressure to pass through the conduit 90 to the rod end side of thecylinder 264. The piston 266 will be retracted moving the mode controlvalve 262 to the right as viewed in FIG. 1. This position of the modecontrol cylinder will be maintained as long as the station selectorvalve is in the rear position irrespective of the manipulation of themode selector valve 270 in the rear station. The mode selector valve 270will therefore direct air pressure to the selected ends of the modecontrol cylinder 64 in order to determine the position of the modecontrol valve 62, which will determine the mode of steering for thevehicle. In its centered twowheel position, the mode selector valve 270will connect both conduits 78 and 72 with the atmosphere through theconduit 284. This will permit the springs 68 and 69 in the cylinder 64to center the piston 66 and the valve 62. When the mode selector valveis shifted to the crab position, conduit 46 will be connected with theconduit 272 while the conduit 278 will be connected with atmospherethrough the conduit 284. The presence of high pressure in the head endof the cylinder 64 will cause the piston 66 to be extended moving themode control valve 62 to the right. When the mode selector valve 270 ismoved to the four-wheel position, the conduit 46 will be connected withthe conduit 278 while the conduit 272 will be vented to atmospherethrough the conduit 284. The presence of high pressure in the conduit278 will cause the piston 66 to be retracted moving the valve 62 to theleft. With the station selector valve 38 in the rear position,manipulation of the mode selector valve 70 in the front station 10 willhave no effect on either of the mode control cylinders 64 and 264. Thisis because the conduit 44 is vented to atmosphere through the conduit 48and the presence pressure in the conduit 272 causes the ball check valve88 to be seated sealing off the conduit 80.

Considering first the front axle. which is indicated generally at 92, apair of steerable wheels, one of which is shown at 94 is pivotable aboutan upright axis defined by the pin 96 through a steering arm 98. Asensing cylinder 100 includes a piston 102 which is centered within thecylinder by means of springs 104 and 106. A piston rod 108 is connectedto the piston 102 and extends in each direction beyond the piston toprovide equal displacements. One end of the rod is connected with a mainpower steering valve 110. The cylinder 100 has an extension 101 which ispivotally connected to the steering arm 98. A conduit 112 extends fromthe mode control valve 62 to one end of the cylinder 100 and a secondconduit 114 extends from the mode control valve 62 to the other end ofthe cylinder 100. A steering ram 116 has a piston 118 which is pivotallyattached to the steering arm 98. A conduit 120 connects with the mainpower steering valve 110 and with the rod end side of the cylinder 116and a second conduit 122 connects between the valve 110 and the head endside of the cylinder 116. A conduit 124 provides a connection betweenthe main steering pump 126 and the valve 110. Another conduit 128provides a return from the valve 1 to the reservoir 52. When hydraulicpressure is present in the conduit 114, the piston 102 and the rod 108will be shifted against the bias of the spring 106 toward the rightcausing the valve 110 to shift in that direction. Since movement of thevalve 110 is limited to a small fraction of an inch, the piston 102 willbecome fixed and the cylinder 100 will be moved upward and to the left.The steering arm 98 and the wheel 94 will be pivoted counterclockwise.Movement of the piston rod 108 in this direction will cause the mainpower steering valve 110 to be moved downward and to the right, wherebythe conduit 124 will be connected with the conduit 120 while the conduit122 will be connected with the reservoir through the conduit 128. Thepressure in conduit 120 will be communicated to the head end side of theram 116 causing the piston 118 to be retracted. Retraction of the piston118 will also cause the wheel 94 to be pivoted in a counterclockwisedirection about the pivot pin 96. The presence of pressure in theconduit 112 will have the opposite effect. That is, the piston 102 willbe shifted upward and the cylinder 100 will be shifted downward causingthe wheel 94 to be pivoted clockwise, while simultaneously shifting thevalve 110 so that the conduit 124 is connected with the conduit 122 andthe conduit 120 with the conduit 128. The hydraulic fluid from the pump126 will then be available to extend the piston 118 and assist thesensing cylinder in turning the wheel 94 counterclockwise. The end towhich and the amount of pressure admitted to the sensingcylinder by thevalve 50 is determined by the direction and degree of rotation of thehand pump. Once the wheel 94 has attained a position such that the forceof the compressed spring within the cylinder is equal to this pressure,the next incremental movement of the steering ram will create a greaterspring force which will urge the valve 110 to its center position,although not completely centering the piston 102 within the cylinder100. One of the springs will, therefore, be compressed. With the valve110 centered the steering action will cease and the steering ramhydraulically locked in position.

The action of the rear axle components numbered 292-328 are indenticalwith that of the comperable components with corresponding referencenumbers of value 200 less on the front axle. However, when the selectedstation has been in either crab or 4-wheel steer and the mode selectorvalve in that station is moved to 2-wheel steer the mode controlcylinder on the end opposite the selected station will be centeredcausing the associated mode control valve to be centered. In itscentered position, the mode control valves connect the two conduitsleading to the sensing cylinder. If the axle on the end opposite theselected station has its wheels in other than the straight aheadposition, the interconnection of the two ends of the sensing cylinderwill permit the springs therein to attempt to center the piston withinthe cylinder. This action will shift the main power steering valve in adirection to direct hydraulic fluid from the main power steering pump tothe steering ram in order to pivot the wheels to a straight aheadposition.

Referring now to the preferred manner of supplying the hydraulic fluidfor the main power steering valves shown in FIG. 2, the vehicle isprovided with a front engine 400 and a rear engine 402. A pair of pumps404 and 406 are driven by the front engine 400. The pumps 404 and 406are connected with the reservoir through conduits 408 and 410,respectively. A conduit 412 connects with the output of the pump 404 andconnects with the conduit 124 communicating with the main power steeringvalve 110. A one-way check valve 414 is provided in the conduit 412 andpermits fluid flow only from the pump 404 toward the conduit 124. Aconduit 416 connects with the pump 406 and with the conduit 324 leadingto the main power steering valve 310 on the rear axle. A one-way checkvalve 418 is provided in the conduit 416 and permits fluid flow onlyfrom the pump 406 to the conduit 324. A pair of pumps 420 and 422 aredriven by the rear engine 402. Conduits 424 and 426 connect between thereservoir 52 and the pumps 420 and 422, respectively. A conduit 428connects with the output of pump 420 and with the conduit 124. A onewaycheck valve 430 is provided in the conduit 428 and permits fluid flowonly from the pump 420 toward the conduit 124. A conduit 432 connectswith the pump 422 and with the conduit 324. A one-way check valve 434 isprovided in the conduit 432 and permits fluid fow only from the pump 422toward the conduit 324.

The pump arrangement as described above, will provide hydraulic fuidunder pressure to both of the conduits 124 and 324 even though only oneof the engines 400 and 402 are operating. This permits all three modesof steering, which necessitates actuation of both axles for the crabsteer and four-wheel steer modes, when one engine has been disabled oris otherwise not functioning. The pumps 404, 406, 420 and 422 replacethe pumps indicated by the numerals 126, 326 and 54 in the system shownin FIG. 1. While FIG. 2 shows the connections necessary to replace thepumps 126 and 326, it will be obvious to one of skill in the art thatone of the two pumps 404 and 406 and one of the two pumps 420 and 422may be joined with a double check valve arrangement to supply hydraulicfluid to the conduit 56 of FIG. 1.

Referring now to the preferred form of sensing cylinder, which would beutilized for the components indicated by the numeral and 300 in theembodiments of FIGS. 1 and 2, the sensing cylinder indicated generallyat 500 is provided with a piston 502 which is sealingly secured byconventional means to a piston rod 504. The piston rod 504 extends oneither side of the piston 502 a sufficient distance in order to provideequal displacement of hydraulic fluid in both directions of movement.One end of the piston rod is secured to an outer sleeve 506 and througha coupling means 508 to the main power steering valve, such as thoseindicated by the reference numerals 110 and 310 in FIG. 1. A pair ofglands 510 and 512 are slidable on the piston rod 504 and are providedwith conventional seals to prevent leakage therebetween. An outer tube514 is secured between the two glands 510 and 512. A compression spring516 is positioned within the sleeve 506 and encircles the outercircumference of the tube 514. A pair of spacer elements 518 and 520 arepositioned between the sleeve 506 and the outer tube 514 and areengageable by the compression spring 516. Each of the spacer elements518 and 520 are provided with inserts 522, which preferably are of a lowstatic coefficient of friction material such as polytetrafluroethylene,and are engageable with the inner surface of the sleeve 506 and theouter surface of the outer tube 514. The spacers serve to position theouter tube 514 with respect to the sleeve 506 and the inserts 522readily permit relative sliding between the spacers 518 and 520 and thesleeve 506 and the tube 514. A pair of snap rings 524 are positioned onthe outer sides of the spacers 518 and 520 and engage grooves formed onthe inner periphery of the sleeve 506. A similar pair of snap rings 526engage grooves formed in the outer surface of the outer tube 514. Thecompression spring 516 urges the spacer elements into contact with thesnap rings 524 and 526. Movement of the tube 514 in either directionrelative to the sleeve 506 will cause compression of the spring 516. Aport 528 in the gland 512 provides fluid communication to the right handside of the piston 502 as viewed in FIG. 3. Fluid communication to theother side of the piston 502 is provided through a port 530 whichcommunicates with an annular space 532 formed by an inner tube 534secured between the glands 510 and 512 and having a smaller radius thanthe inner surface of the outer tube 514. The piston 502 sealinglyengages the inner surface of the inner tube 534. Openings 536 permitfluid communication be tween the interior of the inner tube 534 and theannular space 532.

It can be seen that if the piston rod 504 is restrained, the admissionof hydraulic fluid under pressure through the port 528 will cause theglands 512 and 510 and the tubes 514 and 534 to be moved toward theright as viewed in FIG. 3, while the admission of hydraulic fluidpressure through the port 530 will cause both tubes and both glands tomove as a unit to the left. A connector member 538 is secured to thegland 512 and is pivotally connectable to one of the steering arms suchas 98 or 298.

As explained previously with respect to the inserts 522, it is importantthat the sensing cylinder be readily actuated in order to provide goodsteering sensitivity, and for this reason it is highly desirable tomaintain friction between the moveable parts at a minimum. Sincecorrosion is a large contributing factor to friction, means are providedto minimize the possibility of corrosion. For this purpose, acollapsible boot 540 is secured at one end to the outer surface of thesleeve 506 and at its other end to the gland 512. This boot 540precludes the entrance of contaminants to the outer surface of the outertube. In addition, the frictional forces are maintained at a minimum bychrome plating the inner surface of the sleeve 506 and the outer surfaceof the outer tube 514. This permits the polytetrafluroethylene rings 522to be in contact with a smooth surface of relative corrosion resistanceand maintains the coefficient of friction between the teflon rings 522and the surfaces at a minimum.

While preferred embodiments have been disclosed with respect to thegeneral steering system and component portions thereof, it is to beunderstood that various changes and modifications may be made withoutdeparting from the spirit of the invention as defined by the scope ofthe appended claims.

What is claimed is:

1. In a sensing cylinder for a power steering mechanism associated witha steerable axle including a steering arm, the improvement comprising:

a piston including a rod;

a tube slidably engageable with the piston;

gland means secured to each end of the tube and sealingly engaging therod;

connector means attached to one of the gland means and capable of beingpivotally attached to the steering arm;

a sleeve secured to the rod;

spring means between the tube and the sleeve;

and retainer means engageable with the spring means the tube and thesleeve and capable of compressing the spring means whenever the tubemeans is moved in either direction from the position in which the pistonis centered in the tube.

2. The invention according to claim 1, and further comprising:

a boot means connected between the sleeve and said one gland means.

3. The invention according to claim 2, wherein the facing surfaces ofsaid tube and sleeve are plated with a material to resist corrosion.

4. The invention according to claim 3, and further comprising:

insert rings in said retaining means of a material having a lowcoefficient of static friction.

5. The invention according to claim 4, wherein said insert rings aremade of polytetrafluorethylene.

1. In a sensing cylinder for a power steering mechanism associated witha steerable axle including a steering arm, the improvement comprising: apiston including a rod; a tube slidably engageable with the piston;gland means secured to each end of the tube and sealingly engaging therod; connector means attached to one of the gland means and capable ofbeing pivotally attached to the steering arm; a sleeve secured to therod; spring means between the tube and the sleeve; and retainer meansengageable with the spring means the tube and the sleeve and capable ofcompressing the spring means whenever the tube means is moved in eitherdirection from the position in which the piston is centered in the tube.2. The invention according to claim 1, and further comprising: a bootmeans connected between the sleeve and said one gland means.
 3. Theinvention according to claim 2, wherein the facing surfaces of said tubeand sleeve are plated with a material to resist corrosion.
 4. Theinvention according to claim 3, and further comprising: insert rings insaid retaining means of a material having a low coefficient of staticfriction.
 5. The invention according to claim 4, wherein said insertrings are made of polytetrafluorethylene.